When curves or bends existing on the surfaces of samples such as semiconductor wafers, electronic substrates and steel plates have any effects on the properties of products, there is a need to measure the curves or the bends of relevant products.
For example, when laser beam is projected on a sample as an inspection object, using a laser distance measurement sensor, and a distance between the measurement sensor and the object is measured by receiving a laser beam reflected from the object, and if the measured distance is constant, it may be determined that the object is flat.
However, when the laser distance measurement sensor is used, there is a disadvantage in that it is very expensive to install the laser distance measurement sensor, and a control is required to move the laser distance measurement sensor for application to a broader scope.
Another disadvantage is that inspection time is lengthened, because a small number of laser distance measurement sensors are used to inspect an object. As a conventional apparatus for inspecting a surface of an object, Korea Registered Patent Publication No.: 0564323 is disclosed with a technique to measure a bend generated on an object, using a laser distance measurement sensor. However, the Korea Registered Patent Publication No.: 0564323 is still fraught with the limitations possessed by the laser distance measurement sensor.